The invention relates to an apparatus for detecting containers having at least one property deviating from a previously set standard, said containers comprising a convex, circular symmetrical reflecting upper rim, said apparatus comprising: an illumination station and a video camera for forming a video signal corresponding with the video picture of the upper rim of a container to be checked, a video signal processing unit for comparing the video picture with the picture corresponding with the standard previously set, and generating in dependency of the result of said comparison an approval or rejection signal, respectively.
The illumination station may be in the form of annular illumination station for illuminating the upper rim of respective containers conveyed by a transport apparatus, said illumination station illuminating the upper rim due to which the video camera is able to form the picture of the reflection ring of the upper rim. As an alternative use can be made of a technique, in which the broadened upper rim extends a little over a diffusely reflecting surface, e.g. by transporting the containers by two co-operating starwheels, in which the video camera forms a picture of the upper rim and this upper rim remaining non-illuminated. If necessary also use can be made of light transmitted through the bottom, due to which the upper rim forms a shadow against a lighter background. The description following hereafter will, as an explanation of the invention, only relate to the first-mentioned technique, according to which the upper rim reflects light.
The standard in question can be e.g. the smoothness, evenness, annular shape, or the like of the upper rim, which can be important in view of e.g. closing the container, particularly a glass bottle by means of e.g. a crown cap. Further rough surfaces, cracks, broader portions and the like are properties which may be laid down in a standard, deviations of which may give raise to problems during the processing of the containers.
A deviation of a somewhat different category is the possible crookedness of in particular glass bottles. Crookedness in this case can be interpreted as a deviation in the co-axial positioning of the bottom and the plane of the upper rim. As a result of such a deviation, which particularly may exists in glass bottles, as the production thereof is not always in practice a procedure controllable in every respect, when a bottle is positioned under a filling nozzle a deviation of the desired position of the neck with respect to the position of the mouth opening of the filling tube may be caused, due to which the bottle is not filled or insufficiently filled, the filling apparatus can be polluted and in closing the bottle there is a chance that the related cap or cork cannot be placed in the correct manner.
From the European patent application No. 0 046 241 an inspection apparatus is known, in which an analogue video signal is used. A progressing average of subsequent video lines is used as a reference, after which an individual video line is compared with said reference.
Furthermore a European patent application No. 0 101 246 exists, in which a technique is described for assessing the crookedness of glass containers. Experience has taught that with the way of illuminating shown therein, namely through the walls in the direction of the bottom, in particular with dark coloured bottles there is so little light reflected from the bottom into the direction of the video camera positioned above the bottles, that the apparatus is unreliable in practice and for large classes of bottles even not fit for use.
Furthermore reference is made to the German patent application No. 29 16 361 laid open for public inspection, an addition to German patent application No. 28 48 316.
All publications mentioned describe the basic configuration of the apparatus mentioned in the preamble.